[Two Pointers][Valid Palindrome] - Implement solution for Leetcode 125

2_two_pointers/1_valid_palindrome/solution.go

@@ -0,0 +1,49 @@
+package validpalindrome
+
+// Time complexity: O(n)
+// Space complexity: O(n)
+func IsPalindromeReverseString(s string) bool {
+	clean := make([]rune, 0, len(s))
+	for _, r := range s {
+		if (r >= 'a' && r <= 'z') || (r >= '0' && r <= '9') {
+			clean = append(clean, r)
+		} else if r >= 'A' && r <= 'Z' {
+			clean = append(clean, r+32)
+		}
+	}
+	n := len(clean)
+	for i := 0; i < n/2; i++ {
+		if clean[i] != clean[n-1-i] {
+			return false
+		}
+	}
+	return true
+}
+
+// Time complexity: O(n)
+// Space complexity: O(1)
+func IsPalindromeTwoPointers(s string) bool {
+	left, right := 0, len(s)-1
+	for left < right {
+		for left < right && !((s[left] >= 'a' && s[left] <= 'z') || (s[left] >= 'A' && s[left] <= 'Z') || (s[left] >= '0' && s[left] <= '9')) {
+			left++
+		}
+		for left < right && !((s[right] >= 'a' && s[right] <= 'z') || (s[right] >= 'A' && s[right] <= 'Z') || (s[right] >= '0' && s[right] <= '9')) {
+			right--
+		}
+		l := s[left]
+		r := s[right]
+		if l >= 'A' && l <= 'Z' {
+			l += 32
+		}
+		if r >= 'A' && r <= 'Z' {
+			r += 32
+		}
+		if l != r {
+			return false
+		}
+		left++
+		right--
+	}
+	return true
+}

2_two_pointers/1_valid_palindrome/solution_test.go

@@ -0,0 +1,41 @@
+package validpalindrome
+
+import "testing"
+
+func TestIsPalindrome(t *testing.T) {
+	cases := []struct {
+		name     string
+		fn       func(string) bool
+		s        string
+		expected bool
+	}{
+		// IsPalindromeReverseString
+		{"Reverse String - Palindrome with spaces/punctuations", IsPalindromeReverseString, "Was it a car or a cat I saw?", true},
+		{"Reverse String - Not a palindrome", IsPalindromeReverseString, "tab a cat", false},
+		{"Reverse String - Single character", IsPalindromeReverseString, "a", true},
+		{"Reverse String - Empty string", IsPalindromeReverseString, "", true},
+		{"Reverse String - Mixed case palindrome", IsPalindromeReverseString, "Able was I ere I saw Elba", true},
+		{"Reverse String - Only non-alphanumeric", IsPalindromeReverseString, "!!!", true},
+		{"Reverse String - Palindrome with numbers", IsPalindromeReverseString, "12321", true},
+		{"Reverse String - Not palindrome with numbers", IsPalindromeReverseString, "12345", false},
+
+		// IsPalindromeTwoPointers
+		{"Two	Pointers - Palindrome with spaces/punctuations", IsPalindromeTwoPointers, "Was it a car or a cat I saw?", true},
+		{"Two	Pointers - Not a palindrome", IsPalindromeTwoPointers, "tab a cat", false},
+		{"Two	Pointers - Single character", IsPalindromeTwoPointers, "a", true},
+		{"Two	Pointers - Empty string", IsPalindromeTwoPointers, "", true},
+		{"Two	Pointers - Mixed case palindrome", IsPalindromeTwoPointers, "Able was I ere I saw Elba", true},
+		{"Two	Pointers - Only non-alphanumeric", IsPalindromeTwoPointers, "!!!", true},
+		{"Two	Pointers - Palindrome with numbers", IsPalindromeTwoPointers, "12321", true},
+		{"Two	Pointers - Not palindrome with numbers", IsPalindromeTwoPointers, "12345", false},
+	}
+
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			got := c.fn(c.s)
+			if got != c.expected {
+				t.Errorf("%s failed: expected %v, got %v", c.name, c.expected, got)
+			}
+		})
+	}
+}